Cluster tool techniques with improved efficiency

ABSTRACT

The present disclosure relates to some embodiments of a method for improving processing efficiency of a cluster tool. The method comprises transferring a first lot of wafers from a transfer load lock to a designated storage load lock and transferring a second lot of wafers from the transfer load lock to the designated storage load lock while the first lot of wafers is in the transfer load lock or the designated storage load lock. The designated storage load lock has the same structure as the transfer load lock and respectively has an inner load lock portal at an interface with the first transfer chamber and an outer load lock portal on a sidewall of a front end interface. The inner load lock portal of the designated storage load lock is retained opened during processing. The outer load lock portal of the designated storage load lock is retained closed during processing.

REFERENCE TO RELATED APPLICATION

This Application is a Continuation of U.S. application Ser. No.14/798,938, filed on Jul. 14, 2015 (now U.S. Pat. No. 10,510,566, issuedon Dec. 17, 2019), the contents of which are hereby incorporated byreference in their entirety.

BACKGROUND

Cluster tools are used in many aspects of semiconductor processing.Cluster tools have multiple processing chambers which are integrated ina closed environment and which are configured to separately processsemiconductor wafers. Wafers to be processed are transferred in, out,and between the processing chambers by robot arms, which are alsointegrated in the cluster tool. Cluster tools are advantageous in thatthey can streamline processing because multiple wafers can be processedwithin a single tool, and can reduce contamination because wafers areprotected from the ambient environment when transferred betweenprocessing chambers within the cluster tool.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 shows a schematic view of some embodiments of a cluster tool.

FIGS. 2A-2B show flow diagrams of a method of improving processingefficiency of a cluster tool in accordance with some embodiments.

FIGS. 3-13 show a series of schematic views of a processing tool indifferent steps of wafer processing illustrating methods of improvingepitaxial deposition processing efficiency in accordance with someembodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Integrated circuits (ICs) are manufactured by building up successivepatterned layers, such as semiconductor layers, dielectric layers, andmetal layers, on a semiconductor wafer. In an IC fabrication facility(fab), wafers are grouped into lots or batches, which are moved throughvarious tools to form and pattern the various layers on the wafers. Eachlot or batch of wafers can be stored in a wafer carrier, such as a frontopening universal pod (FOUP) or standard mechanical interface (SMIF).The wafer carrier is then used to carry the wafers of a batch or lotbetween various processing tools, often via a conveyor belt or overheadtransfer assembly and/or via lifters, hoists, etc., such that theprocessing tools can carry out suitable processing steps to form thedesired patterned layers to build-up the ICs on the wafers.

One particular type of tool that can process the wafers is a clustertool, such as used for epitaxial deposition for example. When a wafercarrier arrives at a cluster tool, the wafer carrier is placed on aloading port of the cluster tool. While sitting on the loading port, thewafer carrier is opened and the wafers inside the wafer carrier can beexposed to the ambient environment of the fab. A front end transferrobot then removes the wafers from the opened wafer carrier and placesthe wafers into a load lock, which is a relatively small chamber on afront side of the cluster tool. After the wafers have been loaded intothe load lock, the load lock is closed to be isolated from the ambientenvironment (which is typically at atmospheric pressure) and from otherchambers in the cluster tool (which are typically at vacuum). The loadlock is then pumped down to vacuum. An inner portal of the load lock isthen opened, and the wafers are then transferred from the load lock,through the inner portal, and into processing chambers within thecluster tool. Processing chambers can then carry out processing, such asepitaxial deposition, on the wafers. After the processing is completed,the wafers are transferred from the processing chambers back to the loadlock, from which the wafers can be placed back into the wafer carrierand moved onto the next process tool. Suffice it to say, the amount ofprocessing time the wafers experience in the processing chambers issignificant compared to the amount of time needed to transfer the wafersin and out of the cluster tool. Therefore, to improve overall throughputof the cluster tool, it is important to limit the amount of time duringwhich the process chambers are vacant or idle.

Accordingly, the present disclosure relates to improved techniques ofprocessing wafers in cluster tools. In some embodiments, a cluster toolincludes a designated storage area within an inner chamber of thecluster tool behind its load lock. One or more lots of wafers can betemporarily stored within this designated storage area, which acts as anintermediate landing point between processing chambers or between a loadlock and a processing chamber, for example. Compared to prior artapproaches where wafers were only moved directly between a load lock andprocessing chambers, this designated storage area allows for greaterflexibility in how wafers can be moved within the cluster tool to limitthe amount of time when processing chambers are idle or vacant. Thus,the designated storage area helps to improve efficiency of the clustertool, thereby helping to improve the overall throughput of the fab.

FIG. 1 shows a schematic view of a cluster tool 100 in accordance withsome embodiments. The cluster tool 100 comprises a first transferchamber 110 and a second transfer chamber 116, which are connectedthrough a pair of via connector chambers 112 a, 112 b. A number ofprocessing chambers 114 a, 114 b, 114 c, 114 d are arranged about thefirst transfer chamber 110, and a number of pre-clean chambers 108 a,108 b are arranged about the second transfer chamber 116. The processingchambers 114 a-114 d may have portals or seals 132 a-132 d,respectively, which allow the respective processing chambers to performindependent processing steps; and the pre-clean chambers 108 a, 108 bmay also have portals or seals 134 a, 134 b, respectively, which allowthe pre-clean chambers 108 a, 108 b to perform independent cleaningsteps. A transfer load lock 104 and a designated storage chamber 106 arealso present.

As will be appreciated in more detail below, the designated storagechamber 106 helps to streamline processing by providing a temporarylanding/storage area for wafers which have already been processed orwhich are still awaiting processing, while leaving the inner chambers ofthe cluster tool under vacuum. This allows for more flexible processingand more flexible ordering of wafers within the cluster tool whilelimiting exposure of inner chambers 106, 108, 110, 112, 114, 116 to theambient fab environment by limiting the number of times the transferload lock 104 is opened/closed.

During operation of the cluster tool 100, a control unit 118 isconfigured to control transfer robots 111, 115, and 124; portals 103,105, 132, 134; and vacuum pumps for the various chambers according tothe following sequence. The control unit 118 can include a memory and amicroprocessor, as well as servos, actuators, and the like to facilitatethe operation described below. Further, inner chambers 106, 108, 110,112, 114, and 116 of cluster tool 100 are typically retained undercontinuous vacuum during the operation described below.

At the onset of operation, a wafer carrier 126 a is placed on a firstloading port 102 a of the cluster tool 100, and an outer load lockportal 103 is opened while an inner load lock portal 105 remains closedto retain vacuum for the inner chambers of cluster tool 100. The wafercarrier 126 a is opened (i.e., wafers are exposed to ambient fabenvironment 140), and front end transfer robot 124, which is disposedwithin a housing of a front end interface 122, then removes the wafers120 a from the opened wafer carrier 126 a. The front end transfer robot124 moves the wafers 120 a through outer load lock portal 103 and intotransfer load lock 104. After the wafers 120 a have been loaded into thetransfer load lock 104, the outer load lock portal 103 is closed. Thetransfer load lock 104 is then pumped down to vacuum. The inner loadlock portal 105 is then opened, and the wafers 120 a are then picked upby the first transfer robot 111. The first transfer robot 111 can movethe wafers to the pre-clean chambers 108 (line 142), via connectorchambers 112 (line 128), and/or designated storage chamber 106 (line130).

Typically, the first transfer robot 111 initially moves the wafers to apre-clean chamber 108 a (see line 142), where a pre-cleaning routinesuch as a rinse with deionized water, acetone, surfactant, or othercleaning process is used to clean the surface of the wafers 120. Thecleaning routine can also include a photoresist strip process, such as aplasma stripping process, for example.

The first transfer robot 111 can then typically move the wafers 120 a tothe via connection chamber 112 a (line 136). The second transfer robot115 can then pick-up the wafers 120 a from the via connection chamber112 a, and after opening a chamber portal (e.g., 132 d), can place thepre-cleaned wafers into a processing chamber, e.g., 114 d, forprocessing (line 138). After the wafers are placed in the processingchamber 114 d, the chamber portal 132 d can be closed, and theprocessing, such as an epitaxial growth process, can be performed togrow an epitaxial layer on the wafers 120 a. After processing, thechamber portal 132 d is re-opened, and the second transfer robot 115 canplace the processed wafers back in the via connection chamber 112 a.

Notably, depending on the state of processing in the processing chambers114 and other wafers waiting to be processed, the first transfer robot111 may place the processed wafers 120 a into the designated storagechamber 106 until an opportune time arrives to route the wafers back outof the transfer load lock 104. Alternatively, the wafers 120 a may beplaced into the designated storage chamber 106 before being processed,for example, until a processing chamber is available. The designatedstorage chamber 106 may include a wafer rack 150 that includes aplurality of slots or recesses configured to hold individual wafers 120.For example, in FIG. 1, the wafer rack 150 is illustrated as havingvertical sidewalls 152 and horizontal protrusions 154 extendingoutwardly from the vertical sidewalls 152. Vertical spaces betweenneighboring protrusions are greater than the thickness of a wafer, suchthat individual wafers 120 can be stacked in the slots or recesses,respectively, one over another. In FIG. 1's example, wafers from threelots 120 a, 120 b, 120 c are stored in the designated storage chamber106 concurrently. Often, all wafers of a same lot are moved into thecluster tool together through a single use of transfer load lock 104.

The wafer rack 150 has a sufficient number of slots to hold wafers ofmultiple lots concurrently. In some embodiments, fewer wafers can begrouped in each lot in order to improve queue time comparing previousstandard twenty-five wafers lots. In some embodiments, there is one toone, or two to one, correspondence between number of wafers in a lotcorresponds to number of processing chambers 114. For example, for aprocessing tool having four processing chambers, four or eight waferscan be grouped in one lot and there are partial or dedicate lots inwhich only one or two wafers are placed. For example, the wafer rack 150can hold twenty-eight or more wafers. This provides sufficient storageto allow wafers to be flexibly processed within the cluster tool 100 ina pipelined fashion while the transfer load lock 104 can be opened toinsert/remove lots of wafers respectively. This helps to improvethroughput, and also reduces potential contamination which can enterinner chambers of the cluster tool from the ambient fab environment 140through the transfer load lock 104.

In some embodiments, the designated storage chamber 106 has the samestructure as the transfer load lock 104. For example, the designatedstorage chamber 106 may have an outer load lock portal 107 at aninterface with the first transfer chamber 110, similar to the outer loadlock portal 103 of the transfer load lock 104. The designated storagechamber 106 may also have an inner load lock portal 109 at an interfacewith the front end interface 122, similar to the inner load lock portal105 of the transfer load lock 104. Whereas, in some embodiments, wafersmay be moved solely between the designated storage chamber 106 and thefirst transfer chamber 110 by the first transfer robot 111, wafers arenot be moved between the designated storage chamber 106 and the frontend interface 122. The outer load lock portal 107 of the designatedstorage chamber 106 may be retained fixedly closed during processingwithout allowing wafers to be transferred from designated storagechamber 106 to ports 102 a-102 c by front end robot 124. The inner loadlock portal 109 of the designated storage chamber 106 may be retainedfixedly opened during processing, since the vacuum environment of thedesignated storage chamber 106 would not be broken without using loadlock transfer function to and from the front end interface 122.

As described in detail below, similar processes as above can be repeatedto load and unload all lots of wafers for processing. In someembodiments, multiple lots of wafers can be transferred from thetransfer load lock 104 and stored in the designated storage chamber 106simultaneously. An outer load lock portal 107 at an interface of thedesignated storage chamber 106 and the front end interface 122 is keptclosed during the processing of those multiple lots of wafers. Themaximum lots that can be stored may depend on amount of load ports 102available. Depending on amount of wafers and sequence of the lots, insome embodiments, wafers of different lots can be transferred to theepitaxial deposition chambers 114 in succession in one batch as long asthere are epitaxial deposition chambers available; and/or wafers of thesame lot may need to be divided to across multiple different epitaxialdeposition chambers for processing. If wafers of multiple lots arefinished successively, these lots of wafers can be sent out from thetransfer load lock 104 together (i.e., during a single opening andclosing of the transfer load lock 104).

FIGS. 2A-2B show flow diagrams 200 a, 200 b of a method of improvingprocessing efficiency of a cluster tool in accordance with someembodiments. In the flow diagram, as well as in the schematic viewsfollowing, the cluster tool is described in the context of an epitaxialdeposition cluster tool. It will be appreciated that this epitaxialdeposition cluster tool, which includes a number of epitaxial depositionchambers, is a non-limiting example and other types of processingchambers, such as other deposition tools or etching tools arecontemplated as falling within the scope of this disclosure.

While disclosed method is illustrated and described below as a series ofacts or events, it will be appreciated that the illustrated ordering ofsuch acts or events are not to be interpreted in a limiting sense. Forexample, some acts may occur in different orders and/or concurrentlywith other acts or events apart from those illustrated and/or describedherein. In addition, not all illustrated acts may be required toimplement one or more aspects or embodiments of the description herein.Further, one or more of the acts depicted herein may be carried out inone or more separate acts and/or phases.

At action 202, as illustrated in action 204 and action 206 below, afirst lot of wafers is loaded to a designated storage chamber.

At action 204, the first lot of wafers is sent from first load port to atransfer load lock.

At action 206, the first lot of wafers is transferred from the transferload lock to the designated storage chamber.

At action 208, the first lot of wafers is processed in epitaxialdeposition chambers.

At action 210, as illustrated in action 212 and action 214 below, secondand third lots of wafers are loaded to the designated storage chamber.

At action 212, the second and third lots of wafers are sent from secondand third load ports to the transfer load lock.

At action 214, the second and third lots of wafers are transferred fromthe transfer load lock to the designated storage chamber.

At action 216, as illustrated in action 218 and action 220 below, secondlot and a first group of third lot of wafers are processed in epitaxialdeposition chambers.

At action 218, first lot of wafers is transferred from process chambersto the designated storage chamber.

At action 220, second lot and a first group of third lot of wafers aretransferred from the designated storage chamber to epitaxial depositionchambers.

At action 222, as illustrated in action 224 and action 226 below, firstlot of wafers is unloaded from the cluster tool and fourth lot of wafersis loaded to the designated storage chamber.

At action 224, the first lot of wafers is transferred to the first loadport through the transfer load lock.

At action 226, a fourth lot of wafers is sent to the designated storagechamber from first port through the transfer load lock.

At action 228, as illustrated in action 230 and action 232 below, theremainder of third lot and the fourth lot of wafers are processed inepitaxial deposition chambers.

At action 230, the second lot and the first group of third lot of wafersare transferred back to the designated storage chamber.

At action 232, the remainder of third lot and the fourth lot of wafersare transferred from the designated storage chamber to epitaxialdeposition chambers.

At action 234, as illustrated in action 236 and action 238 below, thesecond lot of wafers is unloaded from the cluster tool and a fifth lotof wafers is loaded to the designated storage chamber.

At action 236, the second lot of wafers is transferred to the secondload port through the transfer load lock.

At action 238, the fifth lot of wafers is sent to the designated storagechamber from the second port through the transfer load lock.

At action 240, as illustrated in action 242, action 244 and action 246below, the fifth lot of wafers is processed in epitaxial depositionchambers.

At action 242, the first group of fifth lot of wafers is transferred tovacant epitaxial deposition chamber.

At action 244, the remainder of third lot and the fourth lot of wafersare transferred to the designated storage chamber from epitaxialdeposition chambers.

At action 246, the remainder of fifth lot of wafers is transferred fromthe designated storage chamber to epitaxial deposition chambers.

At action 248, as illustrated in action 250 and action 252 below, thethird and fourth lots of wafers are unloaded from the cluster tool and asixth and seventh lots of wafers are loaded to the designated storagechamber.

At action 250, the third and fourth lots of wafers are transferred tothe third and first load ports through the transfer load lock.

At action 252, the sixth and seventh lots of wafers are sent to thedesignated storage chamber from the third and first ports through thetransfer load lock.

At action 254, as illustrated in action 256 and action 258 below, thesixth lot of wafers is processed in epitaxial deposition chambers.

At action 256, the fifth lot of wafers is transferred back to thedesignated storage chamber.

At action 258, the sixth lot of wafers is transferred from thedesignated storage chamber to epitaxial deposition chambers.

FIGS. 3-13 show a series of schematic views of a processing tool indifferent steps of wafer processing illustrating methods of improvingepitaxial deposition processing efficiency in accordance with someembodiments. Although FIGS. 3-13 are described in relation to method200, it will be appreciated that the structures disclosed in FIGS. 3-13are not limited to such a method 200, but instead may stand alone asstructures independent of the method. Similarly, although the method isdescribed in relation to FIGS. 3-13, it will be appreciated that themethod is not limited to the structures disclosed in FIGS. 3-13, butinstead may stand alone independent of the structures disclosed in FIGS.3-13.

FIG. 3 illustrates some embodiments of a schematic view 300 of aprocessing tool corresponding to action 202, action 204 and action 206.

As illustrated by schematic view 300, a first lot 120 a of wafers isloaded to a designated storage chamber 106. First, an outer load lockportal 103 of the transfer load lock 104 is opened to have the first lot120 a of wafers sent from a first load port 102 a to the transfer loadlock 104 by a front end transfer robot 124. During this process an innerload lock portal 105 of the transfer load lock 104 remains closed toseal the processing tool from the ambient environment. Then, the outerload lock portal 103 is closed and the transfer load lock 104 is pumpedto be closed to an internal environment of the processing tool. Then,the first lot 120 a of wafers is transferred from the transfer load lock104 to the designated storage chamber 106 by a first transfer robot 111of the first transfer chamber 110.

FIG. 4 illustrates some embodiments of a schematic view 400 of aprocessing tool corresponding to action 208.

As illustrated by schematic view 400, the first lot 120 a of wafers isprocessed in epitaxial deposition chambers 114. In some embodiments, theepitaxial deposition chambers 114 can be a low-temperature orplasma-based chamber. The epitaxial deposition chambers 114 can be usedfor substrate formation or n-type or p-type doping layer formation. Insome embodiments, prior to transferring to the epitaxial depositionchambers 114, the first lot 120 a of wafers are transferred from thedesignated storage chamber 106 to a pre-clean chamber 108 for apre-clean process and then transferred to a via connector chamber 112 bythe first transfer robot 111. Then, the first lot 120 a of wafers istransferred to the epitaxial deposition chambers 114 using a secondtransfer robot 115 of a second transfer chamber 116 after the pre-cleanprocess for an epitaxial growth process. In some embodiments, fourepitaxial deposition chambers 114 a, 114 b, 114 c, 114 d are attached tothe second transfer chamber 116. In many instances, wafers 120 (e.g. thefirst lot 120 a of wafers) can take the form of a disc-like wafer havinga diameter of 1-inch (25 mm); 2-inch (51 mm); 3-inch (76 mm); 4-inch(100 mm); 5-inch (130 mm) or 125 mm (4.9 inch); 150 mm (5.9 inch,usually referred to as “6 inch”); 200 mm (7.9 inch, usually referred toas “8 inch”); 300 mm (11.8 inch, usually referred to as “12 inch”); or450 mm (17.7 inch, usually referred to as “18 inch”); for example. Forpurposes of illustration, examples are given for only one wafer beingprocessed in an epitaxial deposition chamber at one time, which benefitsuniformity of formed film, but processing multiple wafers a time isamenable. In some embodiments, the first lot 120 a of wafers has fourwafers respectively sent to the four epitaxial deposition chambers 114a, 114 b, 114 c and 114 d in succession. In some other embodiments, thefirst lot 120 a of wafers has eight wafers, and four of which areprocessed first and sent back and stay in the designated storage chamber106 while the other four are sent to epitaxial deposition chambers 114for processing.

FIG. 5 illustrates some embodiments of a schematic view 500 of aprocessing tool corresponding to action 210, action 212 and action 214.

As illustrated by schematic view 500, a second lot 120 b and a third lot120 c of wafers are loaded to the designated storage chamber 106. Inthis example, the second lot 120 b is a partial lot having two wafersand the third lot 120 c has four wafers. Similar as above loadingprocess of the first lot 120 a, the second lot 120 b and third lot 120 cof wafers are sent from second load port 102 b and third load port 102 cby a front end transfer robot 124 arranged in a front end interface 122,to the transfer load lock 104, which is sealed from cluster toolenvironment by the inner load lock portal 105. Then, the transfer loadlock is sealed from the front end interface 122 by closing the outerload lock portal 103, and the transfer load lock 104 is pumped to make apressure of the transfer load lock to be close to the cluster toolenvironment. Then, the transfer load lock 104 is opened to the clustertool environment and the second lot 120 b and third lot 120 c of wafersare transferred from the transfer load lock 104 to the designatedstorage chamber 106 by the first transfer robot 111.

FIG. 6 illustrates some embodiments of a schematic view 600 of aprocessing tool corresponding to action 216, action 218 and action 220.

As illustrated by schematic view 600, the second lot 120 b and a firstgroup of third lot 120 c of wafers are processed in epitaxial depositionchambers 114. The first lot 120 a of wafers is transferred fromepitaxial deposition chambers 114 to the designated storage chamber 106.Two wafers of the second lot 120 b are exchanged with two wafers of thefirst lot of wafers to be processed in a first epitaxial depositionchamber 114 a and a second epitaxial deposition chamber 114 b. A firsttwo wafers of third lot 120 c are transferred from the designatedstorage chamber 106 to exchange with the other two wafers of the firstlot 120 a to be processed in a third epitaxial deposition chamber 114 cand a fourth epitaxial deposition chamber 114 d.

FIG. 7 illustrates some embodiments of a schematic view 700 of aprocessing tool corresponding to action 222, action 224 and action 226.

As illustrated by schematic view 700, the first lot 120 a of wafers isunloaded from the cluster tool and in exchange a fourth lot 120 d ofwafers is loaded to the designated storage chamber 106. The inner loadlock portal 105 of the transfer load lock 104 is opened and the firstlot 120 a of wafers is transferred to the transfer load lock 104 by thefirst transfer robot 111. Then the transfer load lock 104 is sealed fromcluster tool environment by closing the inner load lock portal 105 andopened to the front end interface 122. The first lot 120 a of wafers istransferred to the first load port 102 a through the transfer load lock104. The fourth lot 120 d of wafers is sent to the designated storagechamber 106 from the first load port 102 a through the transfer loadlock 104. In this example, the fourth lot 120 d is a partial lot hasonly one wafer.

FIG. 8 illustrates some embodiments of a schematic view 800 of aprocessing tool corresponding to action 228, action 230 and action 232.

As illustrated by schematic view 800, remaining wafers of the third lot120 c and the wafer of the fourth lot 120 d of wafers are processed inepitaxial deposition chambers 114. Wafers of the second lot 120 b aretransferred back to the designated storage chamber 106 in successionfrom the first epitaxial deposition chamber 114 a and the secondepitaxial deposition chamber 114 b, in exchange with the remaining twowafers of the third lot 120 c. And the first two wafers of third lot ofwafers are transferred back to the designated storage chamber 106 insuccession from the third epitaxial deposition chamber 114 c and thefourth epitaxial deposition chamber 114 d. The wafer of the fourth lot120 d is transferred from the designated storage chamber 106 to thethird epitaxial deposition chamber 114 c. The fourth epitaxialdeposition chamber 114 d stays vacant until the second lot 120 b is sentout to exchange more wafers in to the designated storage chamber 106 forprocessing.

FIG. 9 illustrates some embodiments of a schematic view 900 of aprocessing tool corresponding to action 234, action 236 and action 238.

As illustrated by schematic view 900, the second lot 120 b of wafers isunloaded from the cluster tool and in exchange a fifth lot 120 f ofwafers is loaded to the designated storage chamber 106. The second lot120 b of wafers is transferred to the second load port 102 b through thetransfer load lock 104. The fifth lot 120 f of wafers is sent to thedesignated storage chamber 106 from the second load port 102 b throughthe transfer load lock 104. In this example, the fifth lot 120 e is afull lot having four or eight wafers.

FIGS. 10-11 illustrate some embodiments of schematic views 1000, 1100 ofa processing tool corresponding to action 240, action 242, action 244and action 246.

As illustrated by schematic views 1000 and 1100, the fifth lot 120 e ofwafers is processed in epitaxial deposition chambers 114. As illustratedby schematic view 1000, the first one of the fifth lot 120 e is firsttransferred to the vacant fourth epitaxial deposition chamber 114 d. Asillustrated by schematic view 1100, then the remaining two wafers of thethird lot 120 c and the one wafer of fourth lot 120 d are transferredback to the designated storage chamber 106, in exchange the remainingtwo of the fifth lot 120 e of wafers to first, second and thirdepitaxial deposition chambers 114 a-114 c.

FIG. 12 illustrates some embodiments of a schematic view 1200 of aprocessing tool corresponding to action 248, action 250 and action 252.

As illustrated by schematic view 1200, the third lot 120 c and thefourth lot 120 d of wafers are unloaded from the cluster tool and inexchange a sixth lot 120 f and a seventh lot 120 g of wafers are loadedto the designated storage chamber 106. The third lot 120 c and thefourth lot 120 d of wafers are transferred to the third load port 102 cand the first load port 102 a through the transfer load lock 104together in a batch. The sixth lot 120 f and a seventh lot 120 g ofwafers are sent to the designated storage chamber 106 from the thirdload port 102 c and the first load port 102 a through the transfer loadlock 104 together in a batch.

FIG. 13 illustrates some embodiments of a schematic view 1300 of aprocessing tool corresponding to action 254, action 256 and action 258.

As illustrated by schematic view 1300, the sixth lot 120 f of wafers isprocessed in epitaxial deposition chambers. The fifth lot 120 e ofwafers is transferred back to the designated storage chamber 106. Thesixth lot of wafers is transferred from the designated storage chamber106 to the pre-clean chamber 108 and to epitaxial deposition chambers114. More wafers can then be processed using similar mechanics.

Thus, the present disclosure relates to optimized techniques to improveepitaxial deposition processing efficiency and queue time. The wafersare sent to a cluster tool by small lots having less than ten wafers ineach lot. The lots of wafers are sent to a transfer load lock from afront end interface first. Then the lots of wafers are transferred to adesignated storage chamber to wait for processing. Multiple lots ofwafers can be stored in the designated storage chamber for processing,and the lots of wafers can be transferred in and out the tool systemseparately. Thus, improved queue time and efficiency can be achieved.

In some embodiments, the present disclosure relates to a method forimproving processing efficiency of a cluster tool. The method comprisestransferring a first lot of wafers from a first load port to a transferload lock at a first time of loading. The transfer load lock has anouter load lock portal on a sidewall of a front end interface and aninner load lock portal facing a first transfer chamber. The methodfurther comprises transferring a second lot of wafers from a second loadport to the transfer load lock through the outer load lock portal withthe first lot of wafers in the transfer load lock. The first lot ofwafers and the second lot of wafers define a set of transferring wafers.The method further comprises transferring the set of transferring wafersto a designated storage load lock through the first transfer chamber,wherein the designated storage load lock also has an outer load lockportal on the sidewall of the front end interface and an inner load lockportal facing a first transfer chamber and transferring a first group ofthe set of transferring wafers from the designated storage load lock toa pre-clean chamber for a pre-clean process through the first transferchamber using the first transfer robot. The method further comprisestransferring the first group of transferring wafers from the pre-cleanchamber to an epitaxial deposition chamber for an epitaxial growthprocess through a second transfer chamber and transferring the set oftransferring wafers back to the designated storage load lock. The methodfurther comprises transferring the set of transferring wafers from thedesignated storage load lock to the transfer load lock and moving theset of transferring wafers out of the cluster tool at a second time ofunloading. The outer load lock portal of the designated storage loadlock is retained fixedly closed from the first time of loading to thesecond time of unloading. The inner load lock portal of the designatedstorage load lock is retained fixedly open from the first time ofloading to the second time of unloading.

In other embodiments, the present disclosure relates to a method forimproving processing efficiency of a cluster tool. The method comprisessending a first lot of wafers from a first load port to a transfer loadlock in a cluster tool and transferring the first lot of wafers from thetransfer load lock to a designated storage load lock through a firsttransfer chamber in the cluster tool. The method further comprisesending a second lot of wafers from a second load port to the transferload lock and transferring the second lot of wafers from the transferload lock to the designated storage load lock through the first transferchamber while the first lot of wafers is in the transfer load lock orthe designated storage load lock. The designated storage load lock hasthe same structure as the transfer load lock and respectively has aninner load lock portal at an interface with the first transfer chamber.The inner load lock portal of the designated storage load lock isretained opened during processing. The designated storage load lock andthe transfer load lock respectively has an outer load lock portal on asidewall of a front end interface. The outer load lock portal of thedesignated storage load lock is retained closed during processing.

In yet other embodiments, the present disclosure relates to a method forimproving processing efficiency of a cluster tool. The method comprisesproviding a plurality of wafer carriers to a front end interface of acluster tool, wherein each of the plurality of wafer carriers holds alot of wafers and transferring N+1 or more lots of wafers from the frontend interface to a transfer load lock. The method further comprisestransferring the N+1 or more lots of wafers from the transfer load lockto a designated storage load lock in the cluster tool such that the N+1or more lots of wafers are present in the cluster tool at the same time.N is an amount of wafer carriers in the front end interface, wherein theN+1 or more lots of wafers transferred to the designated storage loadlock form initial lots of wafers. The method further comprisestransferring a first group of wafers of the initial lots of wafers fromthe designated storage load lock to a pre-clean chamber in the clustertool for a pre-clean process and transferring the first group of wafersof the initial lots of wafers to an epitaxial deposition chamber in thecluster tool after the pre-clean process. The method further comprisestransferring the first group of wafers of the initial lots of wafers tothe designated storage load lock after the first group of wafers of theinitial lots of wafers has passed through the epitaxial depositionchamber and transferring the first group of wafers of the initial lotsof wafers from the designated storage load lock back to the transferload lock. The method further comprises sending the first group ofwafers of the initial lots of wafers out of the cluster tool from thetransfer load lock. The designated storage load lock has the samestructure as the transfer load lock, and wherein the designated storageload lock and the transfer load lock respectively has an inner load lockportal and an outer load lock portal on a sidewall of the front endinterface. The outer load lock portal of the designated storage loadlock is retained fixedly closed during loading, unloading and processingthe wafer; and wherein the inner load lock portal of the designatedstorage load lock is retained opened during loading, unloading andprocessing the wafer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method for processing wafers in a cluster tool,comprising: transferring a first lot of wafers from a first load port toa transfer load lock at a first time of loading, wherein the transferload lock has an outer load lock portal on a sidewall of a front endinterface and an inner load lock portal facing a first transfer chamber;transferring a second lot of wafers from a second load port to thetransfer load lock through the outer load lock portal with the first lotof wafers in the transfer load lock, wherein the first lot of wafers andthe second lot of wafers define a set of transferring wafers;transferring the set of transferring wafers to a designated storage loadlock through the first transfer chamber, wherein the designated storageload lock also has an outer load lock portal on the sidewall of thefront end interface and an inner load lock portal facing a firsttransfer chamber; transferring a first group of the set of transferringwafers from the designated storage load lock to a pre-clean chamber fora pre-clean process through the first transfer chamber using a firsttransfer robot; transferring the first group of transferring wafers fromthe pre-clean chamber to an epitaxial deposition chamber for anepitaxial growth process through a second transfer chamber; transferringthe set of transferring wafers back to the designated storage load lock;transferring the set of transferring wafers from the designated storageload lock to the transfer load lock; and moving the set of transferringwafers out of the cluster tool at a second time of unloading; whereinthe outer load lock portal of the designated storage load lock isretained fixedly closed from the first time of loading to the secondtime of unloading; and wherein the inner load lock portal of thedesignated storage load lock is retained fixedly open from the firsttime of loading to the second time of unloading.
 2. The method accordingto claim 1, further comprising: transferring the first group of the setof transferring wafers from the epitaxial deposition chamber to a viaconnector chamber after the epitaxial growth process through the secondtransfer chamber; transferring the first group of transferring wafersfrom the via connector chamber to the designated storage load lockthrough the first transfer chamber; transferring the first group oftransferring wafers from the designated storage load lock to thetransfer load lock through the first transfer chamber; and sending thefirst group of transferring wafers out of the cluster tool from thetransfer load lock.
 3. The method according to claim 1, furthercomprising: removing the first group of transferring wafers from theepitaxial deposition chamber; sending a third lot of wafers in thecluster tool from the transfer load lock to the designated storage loadlock while at least some of the set of transferring wafers remain in thedesignated storage load lock; and transferring the remainingtransferring wafers and at least some wafers of the third lot of wafersfrom the designated storage load lock to the epitaxial depositionchamber.
 4. The method according to claim 3, wherein an outer load lockportal of the designated storage load lock is retained fixedly closedduring processing of the first, second and third lots of wafers.
 5. Amethod, comprising: sending a first lot of wafers from a first load portto a transfer load lock in a cluster tool; transferring the first lot ofwafers from the transfer load lock to a designated storage load lockthrough a first transfer chamber in the cluster tool; sending a secondlot of wafers from a second load port to the transfer load lock; andtransferring the second lot of wafers from the transfer load lock to thedesignated storage load lock through the first transfer chamber whilethe first lot of wafers is in the transfer load lock or the designatedstorage load lock; wherein the designated storage load lock has the samestructure as the transfer load lock and respectively has an inner loadlock portal at an interface with the first transfer chamber, wherein theinner load lock portal of the designated storage load lock is retainedopened during processing; wherein the designated storage load lock andthe transfer load lock respectively has an outer load lock portal on asidewall of a front end interface, wherein the outer load lock portal ofthe designated storage load lock is retained closed during processing.6. The method of claim 5, further comprising: sending a third lot ofwafers from the transfer load lock to the designated storage load lockwhile at least some wafers of the second lot of wafers remain in thedesignated storage load lock.
 7. The method of claim 6, wherein each ofthe first, second and third lots contains eight wafers or less.
 8. Themethod of claim 6, wherein each of the first, second and third lotscontains four wafers or less.
 9. The method of claim 6, furthercomprising: transferring the second lot of wafers in succession from thedesignated storage load lock to an epitaxial processing chambercomprising a plurality of epitaxial processing chambers through apre-clean chamber attached to a first transfer chamber; and transferringa first group of the third lot of wafers in succession from thedesignated storage load lock to vacant epitaxial deposition chambersthrough the pre-clean chamber attached to the first transfer chamberwhile the second lot of wafers is being processed in the epitaxialprocessing chamber.
 10. The method of claim 9, further comprising:transferring the second lot of wafers and the first group of the thirdlot of wafers in succession from the epitaxial processing chamber to thedesignated storage load lock; transferring a second group of the thirdlot of wafers in succession from the designated storage load lock tovacant epitaxial processing chambers through the pre-clean chamberattached to the first transfer chamber; and transferring the second lotof wafers from the designated storage load lock to the transfer loadlock while the first group of the third lot of wafers is disposed in thedesignated storage load lock.
 11. The method of claim 5, furthercomprising: transferring the first lot of wafers and the second lot ofwafers in succession from the designated storage load lock to thetransfer load lock; and sending the first lot of wafers and the secondlot of wafers out of the cluster tool in succession from the transferload lock to the first and second load ports respectively.
 12. Themethod of claim 11, further comprising: sending a third lot of wafersand a fourth lot of wafers into the cluster tool respectively from thefirst and second load ports to the transfer load lock; sealing thetransfer load lock and opening the transfer load lock to an ambientenvironment external to the cluster tool; and transferring the third lotof wafers and the fourth lot of wafers in succession from the transferload lock to the designated storage load lock.
 13. The method of claim5, further comprising: transferring the first lot of wafers from thedesignated storage load lock to a pre-clean chamber for a pre-cleanprocess; transferring the first lot of wafers to an epitaxial depositionchamber after the pre-clean process for an epitaxial growth process;transferring the first lot of wafers to the designated storage load lockafter the epitaxial growth process; and transferring the first lot ofwafers from the designated storage load lock to the transfer load lock.14. A method, comprising: providing a plurality of wafer carriers to afront end interface of a cluster tool, wherein each of the plurality ofwafer carriers holds a lot of wafers; transferring N+1 or more lots ofwafers from the front end interface to a transfer load lock;transferring the N+1 or more lots of wafers from the transfer load lockto a designated storage load lock in the cluster tool such that the N+1or more lots of wafers are present in the cluster tool at the same time,wherein N is an amount of wafer carriers in the front end interface,wherein the N+1 or more lots of wafers transferred to the designatedstorage load lock form initial lots of wafers; transferring a firstgroup of wafers of the initial lots of wafers from the designatedstorage load lock to a pre-clean chamber in the cluster tool for apre-clean process; transferring the first group of wafers of the initiallots of wafers to an epitaxial deposition chamber in the cluster toolafter the pre-clean process; transferring the first group of wafers ofthe initial lots of wafers to the designated storage load lock after thefirst group of wafers of the initial lots of wafers has passed throughthe epitaxial deposition chamber; transferring the first group of wafersof the initial lots of wafers from the designated storage load lock backto the transfer load lock; and sending the first group of wafers of theinitial lots of wafers out of the cluster tool from the transfer loadlock; wherein the designated storage load lock has the same structure asthe transfer load lock, and wherein the designated storage load lock andthe transfer load lock respectively has an inner load lock portal and anouter load lock portal on a sidewall of the front end interface; whereinthe outer load lock portal of the designated storage load lock isretained fixedly closed during loading, unloading and processing thewafer; and wherein the inner load lock portal of the designated storageload lock is retained opened during loading, unloading and processingthe wafer.
 15. The method according to claim 14, further comprising:exchanging a first one of the wafer carriers of the plurality of wafercarriers with a first new wafer carrier comprising a first new lot ofwafers; sending the first new lot of wafers in the cluster tool from thetransfer load lock to the designated storage load lock while some of thewafers of the initial lots of wafers are still in the cluster tool;exchanging a second one of the wafer carriers of the plurality of wafercarriers with a second new wafer carrier comprising a second new lot ofwafers; sending the second new lot of wafers in the cluster tool fromthe transfer load lock to the designated storage load lock while atleast some wafers of the first new lot of wafers remain in thedesignated storage load lock; and transferring the first new lot and atleast some wafers of the second new lot respectively from the designatedstorage load lock to epitaxial deposition chambers in succession. 16.The method of claim 15, wherein each of the lots include less than tenwafers.
 17. The method according to claim 15, further comprising:sending the first new lot of wafers out of the cluster tool from thetransfer load lock while the second new lot of wafers remains in theepitaxial deposition chambers.
 18. The method according to claim 14,further comprising: exchanging a first one of the wafer carriers of theplurality of wafer carriers with a first new wafer carrier comprising afirst new lot of wafers and a second one of the wafer carriers of theplurality of wafer carriers with a second new wafer carrier comprising asecond new lot of wafers; sending the first new lot and the second newlot of wafers in the cluster tool from the transfer load lock to thedesignated storage load lock while the first group of wafers of theinitial lot of wafers is still in the cluster tool; transferring thefirst new lot and a first group of the second new lot of wafersrespectively from the designated storage load lock to epitaxialdeposition chambers in succession while at least remaining wafers of thesecond new lot of wafers are still sitting in the designated storageload lock; and sending the first new lot of wafers out of the clustertool from the transfer load lock while the first group of the second newlot of wafers remain in the designated storage and the remaining wafersof the second new lot are processed in the epitaxial depositionchambers.
 19. The method according to claim 14, further comprising:exchanging a first one of the wafer carriers of the plurality of wafercarriers with a first new wafer carrier comprising a first new lot ofwafers and a second one of the wafer carriers of the plurality of wafercarriers with a second new wafer carrier comprising a second new lot ofwafers; sending the first new lot and the second new lot of wafers inthe cluster tool from the transfer load lock to the designated storageload lock while the first group of wafers of the initial lot of wafersis still in the cluster tool; transferring some of the first new lot andthe second new lot of wafers respectively from the designated storageload lock to epitaxial deposition chambers in succession; and sendingthe first new lot and the second new lot of wafers out of the clustertool from the transfer load lock together in a batch.
 20. The methodaccording to claim 14, wherein each wafer processed by the cluster toolis transferred the designated storage load lock from the transfer loadlock prior to processing and is transferred back to the transfer loadlock through the designated storage load lock after processing.